Grid refinement method

ABSTRACT

The present disclosure provides an embodiment of a method, for a lithography process for reducing a critical dimension (CD) by a factor n wherein n&lt;1. The method includes providing a pattern generator having a first pixel size S1 to generate an alternating data grid having a second pixel size S2 that is &lt;S1, wherein the pattern generator includes multiple grid segments configured to offset from each other in a first direction; and scanning the pattern generator in a second direction perpendicular to the first direction during the lithography process such that each subsequent segment of the grid segments is controlled to have a time delay relative to a preceding segment of the grid segments.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a continuation of U.S. Ser. No. 13/722,266, filedDec. 20, 2012 by inventors Wen-Chuan Wang et al., entitled “GRIDREFINEMENT METHOD”, which claims the benefit of U.S. ProvisionalApplication No. 61/623,959, filed Apr. 13, 2012 by inventors Wen-ChuanWang et al., entitled “GRID REFINEMENT METHOD”, each of which is hereinincorporated by reference in its entirety.

The present disclosure is related to the following commonly-assignedU.S. patent application, the entire disclosure of which is incorporatedherein by reference: U.S. Ser. No. 13/368,877 filed Feb. 8, 2012, nowissued U.S. Pat. No. 8,530,121, issued Sep. 10, 2013 to inventorsWen-Chuan Wang et al., for “A MULTIPLE-GRID EXPOSURE METHOD”.

BACKGROUND

The semiconductor integrated circuit (IC) industry has experienced rapidgrowth. In the course of the IC evolution, functional density (i.e., thenumber of interconnected devices per chip area) has generally increasedwhile geometry size (i.e., the smallest component (or line) that can becreated using a fabrication process) has decreased. This scaling downprocess generally provides benefits by increasing production efficiencyand lowering associated costs. Such scaling down has also increased thecomplexity of processing and manufacturing ICs and, for these advancesto be realized, similar developments in IC manufacturing are needed.

For example, as the semiconductor industry has progressed into nanometertechnology process nodes in pursuit of higher device density, higherperformance, and lower costs, stricter demands have been placed onlithography process. For example, techniques such as immersionlithography, multiple patterning, extreme ultraviolet (EUV) lithography,and e-beam lithography have been utilized to support critical dimension(CD) requirements of the smaller devices. Such lithography methods,however, may result in truncation error which adversely effects the CDrequired for the smaller deices. Certain compensation methods, such asincreasing the number of pixels in an exposure grid and pre-exposuredata preparation/computation, have been used to minimize the truncationerror. These compensation methods, however, increase manufacturing timeand cost. Accordingly, although existing lithography methods have beengenerally adequate, they have not been satisfactory in all respects.

BRIEF DESCRIPTION OF THE DRAWINGS

The present disclosure is best understood from the following detaileddescription when read with the accompanying figures. It is emphasizedthat, in accordance with the standard practice in the industry, variousfeatures are not drawn to scale and are used for illustration purposesonly. In fact, the dimensions of the various features may be arbitrarilyincreased or reduced for clarity of discussion.

FIGS. 1˜6 and 8˜9 are schematic views illustrating methods for alithography process, according to aspects of the present disclosure invarious embodiments.

FIG. 7 is a top view of a data grid for a lithography process, accordingto various aspects of the present disclosure in one embodiment.

FIGS. 10˜12 illustrate data grids in top views and formulae for datasignal output, according to various aspects of the present disclosure invarious embodiments.

DETAILED DESCRIPTION

The following disclosure provides many different embodiments, orexamples, for implementing different features of the invention. Specificexamples of components and arrangements are described below to simplifythe present disclosure. These are, of course, merely examples and arenot intended to be limiting. For example, the formation of a firstfeature over or on a second feature in the description that follows mayinclude embodiments in which the first and second features are formed indirect contact, and may also include embodiments in which additionalfeatures may be formed between the first and second features, such thatthe first and second features may not be in direct contact. In addition,the present disclosure may repeat reference numerals and/or letters inthe various examples. This repetition is for the purpose of simplicityand clarity and does not in itself dictate a relationship between thevarious embodiments and/or configurations discussed. Also, thecomponents disclosed herein may be arranged, combined, or configured inways different from the exemplary embodiments shown herein withoutdeparting from the scope of the present disclosure. It is understoodthat those skilled in the art will be able to devise various equivalentsthat, although not explicitly described herein, embody the principles ofthe present invention.

As semiconductor fabrication technologies continue to evolve,lithography processes have been utilized to achieve increasingfunctional densities and decreasing device sizes. One form oflithography is electron beam (e-beam) lithography. In e-beamlithography, an e-beam apparatus emits beams of electrons in a patternedmanner across a surface of a substrate covered with an e-beam sensitiveresist film (or resist film). This process may be referred to as anexposure process. A developing process is subsequently utilized toselectively remove either exposed regions or non-exposed regions of theresist film, depending on the resist film being positive or negative.The developing of the resist film results in a patterned resist film,which may be used as a patterned mask to pattern the substrate (or otherlayers of the substrate) in subsequent fabrication processes.

With reference to FIGS. 1 to 12, a method for lithography process isdescribed below according to various embodiments. FIG. 1 is a schematicview illustrating an exposure method, according to various aspects ofthe present disclosure in one embodiment. In FIG. 1, the diagram 20illustrates that critical dimension (CD) shrinks to smaller dimensionswhen the integrated circuit (IC) fabrications progress to advancedtechnology nodes. Accordingly, the data grid shrinks to smaller pixelsize. The data grid refers to a pattern formed on the resist layer anddefined in a grid structure. Exposure dose (or exposure intensity) canbe changed per data grid and cannot be independently changed in afraction of a data grid. In this embodiment, the data grid shrinksaccordingly such that small feature can be exposed with a suitableresolution. In one example, the CD shrinks from X to nX where n is lessthan 1, such as 0.7. Accordingly, the data grid 22 shrinks to a datagrid 24 by the same factor n. The pixel area shrinks by a factor n².

In the present embodiment, an IC pattern (or IC layout design) istransferred to the resist film by a pattern generator. The patterngenerator is a structure capable of generating a lithography exposurepattern during a lithography exposure process by a lithographyapparatus, such as an e-beam lithography apparatus. In one example, thepattern generator includes a micro-electric mechanical system (MEMS)with multiple pixels, each being independently operable to be “on” (foran exposure dose) or “off” (no exposure). FIG. 1 illustrates a patterngenerator 26 in a top view according to one example. The patterngenerator 26 includes a plurality of pixels arranged in an array. Eachpixel can be independently and dynamically controlled to switch betweentwo states “on” and “off”, representing a signal 1 or 0. For example,when a pixel is in an “on” state, the e-beam can be directed through thepixel. When the pixel is in an “off” state, the e-beam is blocked fromgoing through the pixel. During the lithography process, the e-beam isdirected to the pattern generator, the pattern generator is controlledto independently turn on or off each pixel by a control circuit coupledwith each pixel and addressing each pixel.

Furthermore, when the CD shrinks from X to nX, the pattern generator 26shrinks to a pattern generator 28 by a same factor n. In other words,the pattern generator 26 has a pixel dimension X and the patterngenerator 28 has a pixel dimension nX.

In this embodiment, there are various challenges. First, shrinking thepixel size of the pattern generator is very difficulty or may not beachievable considering each pixel having its own control circuit (pixelcontrol circuit) coupled with the pixel and configured in thecorresponding area of the pixel. Particularly, the pixel control circuitis disposed approximate to an active portion of the pixel (such as amoving element of the pixel) and occupies a certain surface area of thepixel, the shrinking by scaling has its limit due to the surface areaconfliction.

Second, by shrinking the pixel size, the number of pixels in a unit areaof the pattern generator is increased by a factor 1/n². The data used tocontrol the pattern generator are increased by the same factor. As shownin FIG. 1, the data volume is increased by the factor of 1/n² that isgreater than 1. For example, if n is 0.7, the data volume is aboutdoubled.

The method of the FIG. 1 is further described with reference to FIG. 2as a schematic view, according to various aspects of the presentdisclosure in one embodiment. Particularly, the pattern generator andthe data grid before the shrinking are illustrated in the left table 30and the pattern generator and the data grid after the shrinking areillustrated in the right table 31. In the left table 30 prior to theshrinking, the pattern generator 32 includes a plurality of pixels in anarray. In this example, the pattern generator 32 has the pixels arrangedin an orthogonal matrix. The X axis and Y axis are illustrated in FIG. 2as a reference. The pixels of the pattern generator 32 arranges intomultiple rows. Each row spans in the X direction and includes Nx pixels.Similarly, the pixels of the pattern generator 32 arranges into multiplecolumns. Each column spans in the Y direction and includes Ny pixels.Total number of the pixels in the pattern generator is Nx*Ny. Each pixelhas a same dimension G.

During a lithography process, the pattern generator 32 is thusconfigured and scans over the resist film along the Y direction with aspeed V relative to the resist film. The corresponding data grid 34 isillustrated. The pixels in the data grid 34 has a pixel dimension G sameto the pixel dimension of the pattern generator 32. When a field is thusexposed, the pattern generator 32 is stepped to another field, and thesimilar scan is repeated to the next field. The resist film coated onthe substrate is thus exposed with one or more IC patterns are imaged tothe resist film. Each field in the data grid is a strip with widthdefined in the X direction and covers Nx pixels. Each pixel in the datagrid 34 is scanned by Ny pixels in the corresponding column of thepattern generator 32. Thus, the exposure dose (electron intensity) inthat pixel is the collective result of the Ny pixels in thecorresponding column, or the sum of exposure doses of the Ny pixels inthe column of the pattern generator. As noted above, each pixel can beindependently turned on or off, therefore has two exposure doses,respectively represented by full dose (or maximum dose) and none (orminimum dose). With different combinations of the Ny pixels in variousstates (on and off), Ny+1 gray levels are achieved in term of theexposure dose. If the pixel intensity of each pixel in the patterngenerator is represented by 1 for “on” state and “0” for “off” state ina proper unit, the lowest intensity in one pixel of the data grid 34achieved by the pattern generator is 0 and the highest intensity is Ny.All other gray levels 1, 2, . . . , and Ny−1 can be provided by variouscombinations and thus the total Ny+1 gray levels are achieved.

When m bits of data are provided to address gray levels, the total graylevels are 2^(m) as illustrated by gray levels 35 in FIG. 2. The numberof pixels Ny in each column of the pattern generator 32 needs to be2^(m)−1 to provide 2^(m) gray levels. The bit, gray level and number ofpixels (in each column of the pattern generator 32) are furtherillustrated in a table 36. The data volume is proportional to theparameter m, as indicated in the “data volume” of the table 30.

When the pattern generator 32 is scanned over one field of the substratealong the Y direction, the exposed field has a distributed intensity andis represented by the data grid 34. For example, the pixels in the leftcolumn of the pattern generator 32 sequentially scan through a pixel inthe left column of the data grid 34. Similarly, the pixels in the fourthcolumn of the pattern generator 32 sequentially scan through a pixel inthe fourth column of the data grid 34.

In this method, when the CD is scaled down by n, the pattern generator32 is replaced by another pattern generator 37 with a pixel dimensioncorrespondingly reduced to n*G. Corresponding data grid 38 shrinks aswell and has a reduced pixel dimension n*G. Accordingly, the data volumeis increased by a factor 1/n² since the number of pixels per unit areaof the pattern generator 37 is increased by the factor 1/n². The datavolume associated with the pattern generator 37 is proportional to m/n²as indicated in the “data volume” of the table 31.

FIG. 3 is a schematic view of a method 40 for a lithography process withreduced data grid for small CDs but without reducing the pixeldimensions of the pattern generator. The method 40 and the correspondingpattern generator are collectively described with reference to FIG. 3that includes a block 42 for pattern generator, a block 44 for data gridand a block 46 for data signal output. It is still assumed that the CDscales down by a factor n that is less than 1. As one example, theparameter n is 0.5. It is understood that the parameter n can be anyproper value less than 1. Pattern generator 48 is designed to include aplurality of grid segments (or segments) configured along the scandirection that is Y direction. The pixels of the pattern generator 48still remain the same pixel dimension G. In one example, the pixels havea square geometry, the dimensions of the pixels in both X and Ydirections are G. In another embodiment, the pixels have a rectangulargeometry, and the dimension of the pixels in X direction is G. In thepresent example for illustration, the pattern generator 48 includes 4segments labeled as A, B, C and D, respectively. Each segment is shiftedby a fraction of the pixel dimension G along the direction perpendicularto the scan direction or is controlled to have delayed data signaloutput.

The data signal output is the signal sent to the pattern generator 48and controls the respective pixel to response to the pattern data for“on” and “off”. The data signal output is not pattern data itself but aclock signal to control the timing of the pixels. The method 40 includeshow the data signal output is timed to achieve a shift between thesegments along the scan direction and forms a data grid with a reducedpixel size.

Each segment includes a plurality of pixels in an array, such as anarray with multiple rows each spanned in X direction and multiplecolumns each spanned in Y direction. Furthermore, each row includes Nxpixels and each column includes Ny pixels. To achieve 2^(m) gray levels,the number of pixels in each column is 2^(m)−1 or Ny=2^(m)−1.

It is further described how the pattern generator 48 is designed and howa data grid with reduced pixel size is formed without reducing the pixelsize of the pattern generator. Particularly, the pixel size of the datagrid is reduced to n*G but the pixel size of the pattern generator 48remains as G.

As mentioned earlier, the first segment A of the pattern generator 48scans with speed V in the Y direction through a field and forms anexposure pattern in the field and the exposure pattern is defined in afirst data grid 50 (or data grid A). The data grid 50 has the same pixelsize G. The data signal output 60 for the first segment is illustratedin the graph the “data signal output” block 46, where Δt₀ is the time topass one pattern generator pixel during the scan, and t₀ represents timezero for scanning the respective field.

In the present example of the pattern generator 48, the second segment Bis similar to the first segment A but is controlled to have a time delayΔt during the lithography process. Note the pattern generator scans inthe Y direction with a speed V and the travel time to pass one patterngenerator pixel is Δt₀. The travel time to pass one segment of thepattern generator 48 is Ny*Δt₀ or (2^(m)−1)*Δt₀. The data signal outputto the second segment is supposed to be (2^(m)−1)*Δt₀ later than thedata signal output to the first segment if without time delay. Thus theexposure doses from the first segment and second segment aresynchronized to the same pixels in the corresponding data grid. Delayingthe data output signal of the second segment B by Δt, the data outputsignal 62 is actually (2^(m)−1)*Δt₀+Δt later than the data signal output60 to the first segment. Delaying the data output signal of the secondsegment B by Δt, the exposure dose by the second segment offsets fromthe exposure dose of the first segment by a distance Δy=V*Δt in Ydirection. In other words, the exposure dose generated by the secondsegment is defined by another data grid (data grid B) similar to thefirst data grid 50 but has an offset Δy=V*Δt in Y direction. In thepresent case, the Δy is chosen to be G/2 or generally nG. Accordingly,the time delay is chosen to be n*(G/V) or n*Δt₀. The exposure dosedefined in the second data grid B and the exposure dose defined in thefirst data grid A define a collective exposure dose from the segment Aand segment B. The collective exposure dose is defined by a collectivedata grid 52 with reduced pixel dimension in Y direction. The datasignal output 62 for the second segment B is t₀+(2^(m)−1)*Δt₀+Δt asindicated in “data signal output” block 46.

The third segment C of the pattern generator 48 is similar to the secondsegment B but is configured to have an offset to the second segment byΔx in X direction. Δx is a fraction of G, such as G/2 in the presentexample where 1/n=2. The exposure dose from the third segment C isdefined in a data grid C and is similar to the exposure dose from thesecond segment defined in the data grid B but has a shift Δx in Xdirection. A collective exposure dose from the first, second and thirdsegments are summation of the first exposure dose from the firstsegment, the second exposure from the second segment and the thirdexposure dose from the third segment. The collective exposure dose isdefined by the third data grid 54 with reduced pixel dimension in Ydirection and reduced pixel dimension in X direction. The data outputsignal 64 for the third segment C is t₀+2(2^(m)−1)*Δt₀+Δt as indicatedin the “data signal output” block 46.

The fourth segment D of the pattern generator 48 is similar to the thirdsegment C but is controlled to have a time delay Δt during thelithography process relative to the third segment. The exposure dosefrom the fourth segment D is defined in a data grid D and is similar tothe exposure dose from the third segment defined in the data grid C buthas a shift Δy=V*Δt in Y direction. A collective exposure dose from thefirst, second, third and fourth segments are summation of the firstexposure dose from the first segment, the second exposure from thesecond segment, the third exposure dose from the third segment and thefourth exposure dose from the fourth segment. The collective exposuredose is defined by the fourth data grid 56 with further reduced pixeldimension in Y direction and reduced pixel dimension in X direction. Thedata output signal 66 for the fourth segment D is t₀+3(2^(m)−1)*Δt₀+2Δtas indicated in the “data signal output” block 46.

Overall, the collective exposure dose from various segments of thepattern generator 48 defines the collective data grid 56 with reducedpixel dimensions. Particularly, by choosing proper Δx and Δt, the pixeldimensions (in X and Y directions) are reduced to G*n. The pixel area ofthe collective data grid 56 is reduced by a factor n². The data volumeis proportional to m/n². Thus, by implementing the method 40 and thepattern generator 48, the data grid is reduced without reducing thepixel size of the pattern generator 48. The data volume is increased bya factor m/n². It is understood that the pattern generator 48 is only anexample. The pattern generator 48 may include a different number ofsegments each being shifted by Δx and delayed by Δt to the proceedingsegment. When the scaling factor n is a different value, the number ofsegments is changed accordingly. For example, when n is ⅓, the number ofsegments is increased to 9. Generally speaking, the number of segmentsis determined by the factor 1/n².

FIG. 4 is a schematic view of a method 70 for a lithography process withreduced data grid for small CDs but without reducing the pixeldimensions of the pattern generator. The structure of the patterngenerator and the method 70 are collectively described with reference toFIG. 4 that includes a block 72 for pattern generator, a block 74 fordata grid and a block 76 for data signal output. It is still assumedthat the CD scales down by a factor n that is less than 1. In oneexample, the scaling factor n is 0.5.

In the method 70, a pattern generator 78 is used and includes aplurality of segments configured with relative offset or controlled withrelative time delay similar to the pattern generator 48. Particularly,pattern generator 78 is designed to include a plurality of segmentsconfigured along the scan direction that is Y direction. The pixels ofthe pattern generator 78 still remain the same pixel dimension G. In oneexample, the pixels have a square geometry and the dimensions of thepixels in both X and Y directions are G. In another embodiment, thepixels have a rectangular geometry and the dimension of the pixels in Xdirection is G. In the present example for illustration, the patterngenerator 78 includes 4 segments labeled as A, B, C and D, respectively.Each segment is shifted by a fraction of the pixel dimension G along thedirection perpendicular to the scan direction or is controlled to havedelayed data signal output relative to the preceding segment.

Each segment includes a plurality of pixels in an array, such as anarray with multiple rows each spanned in X direction and multiplecolumns each spanned in Y direction. Furthermore, each row includes Nxpixels and each column includes Ny pixels. To achieve 2^(m) gray levels,the number of pixels in each column is 2^(m)−1 or Ny=2^(m)−1.

The similar features and actions are not described for simplicity.However, the pattern generator 78 is different from the patterngenerator 48 since the four segments are configured differently.Specifically, the segment B is configured to have an offset from thesegment A by a distance Δx in the X direction. The segment C is alignedwith the segment A in the X direction and controlled to have a timedelay Δt during the lithography process, causing exposure dose shiftedin the Y direction by Δy=V*Δt. The segment D is configured to have anoffset from the segment C by a distance Δx in the X direction.

The method 70 is different from the method 40 since the method 70 usesthe pattern generator 78 different from the pattern generator 48 andprovides different data signal output for proper time delay during thelithography process. Particularly, the data signal output 90 for thesegment A is t₀. The data signal output 92 for the segment B ist₀+(2^(m)−1)*Δt₀. The data signal output 94 for the segment C ist₀+2(2^(m)−1)*Δt₀+Δt. The data signal output 96 for the segment D ist₀+3(2^(m)−1)*Δt₀+Δt.

The segment A during the lithography process forms a data grid A(labeled as 80) as illustrated in FIG. 4. The pixel dimensions of thedata grid A are same to the pixel dimension G of the pattern generator78. The segment B during the lithography process forms data grid Bsimilar to the data grid A from the segment A but is shifted by Δx in Xdirection. The collective exposure dose from both segments A and B isdefined in a data grid 82 having a reduced pixel dimension in the Xdirection.

The segment C during the lithography process forms data grid C similarto the data grid A from the segment A but is shifted by Δy=V*Δt in Ydirection achieved by the time delay Δt. The collective exposure dosefrom the segments A, B and C is defined in a data grid 84 having areduced pixel dimension in the X direction and a reduced pixel dimensionin the Y direction.

The segment D during the lithography process forms data grid D similarto the data grid C from the segment C but is shifted by Δx in Xdirection. The collective exposure dose from all segments A, B, C and Dis defined in a data grid 86 having a reduced pixel dimension in the Xdirection and a reduced pixel dimension in the Y direction.

Overall, the collective exposure dose from various segments of thepattern generator 78 defines the collective data grid 86 with reducedpixel dimensions. Particularly, by choosing proper Δx (and Δt), thepixel dimension in X direction (and in Y direction) is reduced to G*n.The pixel area of the collective data grid 86 is reduced by a factor n².The data volume is proportional to m/n². Thus, by implementing themethod 70 and the pattern generator 78, the data grid is reduced withoutreducing the pixel size of the pattern generator 78. The data volume isincreased by a factor m/n². It is understood that the pattern generator78 is only an example. When the scaling factor n has a different value,the pattern generator 78 may include a different number of segments eachbeing shifted by Δx or delayed by Δt to the proceeding segment.

FIG. 5 is a schematic view of a method 100 for a lithography processwith reduced data grid for small CDs but without reducing the pixeldimensions of the pattern generator. The method 100 and thecorresponding pattern generator are collectively described withreference to FIG. 5 that includes a block 102 for pattern generator, ablock 104 for data grid and a block 106 for data signal output. It isstill assumed that the CD scales down by a factor n that is less than 1.In one example, the scaling factor n is 0.5.

In the method 100, a pattern generator 108 is used and includes aplurality of segments controlled with relative time delay. Particularly,the pattern generator 108 is designed to include a plurality of segmentsconfigured along the scan direction that is Y direction. The pixels ofthe pattern generator 108 still remain the same pixel dimension G. Inone example, the pixels have a square geometry and the dimensions of thepixels in both X and Y directions are G. In another embodiment, thepixels have a rectangular geometry, and the dimension of the pixels in Xdirection is G. Each segment includes a plurality of pixel rows withalternative shift on the X direction and a set of the segments arecontrolled to have time delay.

In the present example for illustration, the pattern generator 108includes 2 segments referred to as 110 and 112, respectively. Thepattern generator 108 is further described below according to thepresent example. The first segment 110 includes two sets of pixel rowsoriented in the X direction and disposed alternatively in the Ydirection. A first set of pixel rows is referred to as A and a secondset of pixel rows is referred to as B. The first set of pixel rows Aincludes Ny=2^(m)−1 rows and the second set of pixel rows B includesNy=2^(m)−1 rows as well. Each row includes Nx pixels. The second set ofpixel rows B are further configured to have an offset to the first setof pixel rows A by Δx in the X direction.

The second segment 112 is similar to the first segment 110. The secondsegment 112 includes two sets of pixel rows oriented in the X directionand disposed alternatively in the Y direction. In the second segment112, a first set of pixel rows is referred to as C and a second set ofpixel rows is referred to as D. The first set of pixel rows C includesNy=2^(m)−1 rows and the first set of pixel rows D includes Ny=2^(m)−1rows as well. Each row includes Nx pixels. The second set of pixel rowsD are further configured to have an offset to the first set of pixelrows C by Δx in the X direction.

According to the present embodiment in a broader form when the scalingfactor n is any proper value, such as 1/n being 2 or 3, a number of thegrid segments in the pattern generator equals to 1/n. Each of the gridsegments includes a grid array with (2^(m)−1)/n pixels in each columnalong the second direction and the data grid has 2^(m) gray levels. The(2^(m)−1)/n pixels in the column are grouped into (2^(m)−1) groups andeach group includes 1/n pixels configured to offset from each other inthe first direction.

Furthermore, the second segment 112 is controlled to have a time delayΔt during a lithography process, causing exposure dose shifted in the Ydirection by Δy=V*Δt.

The method 100 is different from the method 40 (or the method 70) sincethe method 100 uses the pattern generator 108 different from the patterngenerator 48 (or the pattern generator 78) and provides different datasignal output for proper time delay during the lithography process. Thedata signal output 120 for the first set of pixel rows A in the firstsegment 110 is indicated in the respective graph. The data signal output122 for the second set of pixel rows B in the first segment 110 isindicated in the respective graph. Especially, since the first set ofrows A and the second set of rows B are alternatively disposed in thesame grid segment, The data output signals for the first set (rows A)and the second set (rows B) are alternatively on and off for scanningthe respective portions such that the pattern generator is able toreceive proper signals for the A rows and B rows. Thus, the data outputsignal 120 for the rows A and the data output signal 122 for the rows Btogether constitute a collective data output signal for the firstsegment 110 (including both rows A and rows B) in a same sequence. Moreparticularly, the data output signal 120 is on for a period of time toscan a distance G for its respective pixel while the data output signal122 is off. The data output signal 120 is off while the data outputsignal 122 is on for the same period of time to scan another distancefor its respective pixel. In the present embodiment, the period of timeis G/V=Δt₀. Sequentially, the data output signal 120 is on, off, on,off, . . . while the data output signal 122 is off, on, off, on, . . . .

The start time for the second set of pixel rows B in the first segment110 is different from the start time for the first set of pixel rows Ain the first segment 110 as indicated in the data signal outputs 120 and122. Particularly, the start time for the first set of pixel rows A inthe first segment 110 is t₀, and the start time for the second set ofpixel rows B in the first segment 110 is t₀+Δt₀.

The data signal output 124 for the first set of pixel rows C in thesecond segment 112 is t₀+2(2^(m)−1)*Δt₀+Δt. The data signal output 126for the second set of pixel rows D in the second segment 112 ist₀+[2(2^(m)−1)+1]*Δt₀+Δt. Particularly, the start time for the third setof pixel rows C in the second segment 112 is different from the starttime for the second set of pixel rows D in the second segment 112 asindicated in the signals 124 and 126.

The first set of pixel rows A in the first segment 110 during thelithography process forms a data grid A with a same pixel dimension asthe pixel dimension G of the pattern generator 108. The second set ofpixel rows B in the first segment 110 during the lithography processforms a data grid B with a same pixel dimension G. However, the datagrid B is only shifted from the data grid A in the X direction. Acollective exposure dose from both the first set A and the second set Bis defined by a data grid 114 having a reduced pixel dimension in the Xdirection.

Similarly, the first set of pixel rows C in the second segment 112during the lithography process forms a data grid C with a same pixeldimension as the pixel dimension G of the pattern generator 108. Thesecond set of pixel rows D in the second segment 112 during thelithography process forms a data grid D with a same pixel dimension G.Furthermore, the data grid D is only shifted from the data grid C in theX direction. A collective exposure dose from both the first set C andthe second set D is defined by a data grid having a reduced pixeldimension in the X direction.

However, the data grid from the second segment 112 is different from thedata grid from first segment 110 since there is offset Δy=V*Δt in the Ydirection introduced by the time delay Δt. Furthermore, a collectiveexposure dose from both first segment 110 and second segment 112 isdefined by a data grid 116 having a reduced pixel dimension in the Xdirection and a reduced pixel dimension in the Y direction.

By implementing the pattern generator 108 and the method 100, withoutreducing the pixel size of the pattern generator, the data grid 116generated thereby has a reduced pixel size as n*G where G is the pixelsize of the pattern generator 108 and n is the scaling factor. Thenumber of gray levels in each pixel of the data grid 116 is Ny=2^(m)−1.The data volume is increased by a factor m/n². It is understood that thepattern generator 108 is only an example. When the scaling factor n hasa different value, the pattern generator 108 may include a differentnumber of segments. Each segment has an alternating structure withadjacent rows shifted by Δx in the X direction and a set of the segmentsare controlled to have time delay Δt.

FIG. 6 is a schematic view of a method 130 for a lithography processwith reduced data grid for small CDs but without reducing the pixeldimensions of the pattern generator. The method 130 and thecorresponding pattern generator are collectively described withreference to FIG. 6 that includes a block 132 for pattern generator, ablock 134 for data grid and a block 136 for data signal output. It isstill assumed that the CD scales down by a factor n that is less than 1.In one example, the scaling factor n is 0.5.

In the method 130, a pattern generator 108 is used and includes aplurality of segments controlled with relative time delay. The patterngenerator 108 is similar to the pattern generator 108 of FIG. 5 in termof configuration but is controlled with different data signal output.The detailed description of the pattern generator 108 is not repeatedhere for simplicity.

The method 130 is different from the method 100 since the method 130provides different data signal output for time delay during thelithography process. Particularly, the data signal output 150 for thefirst set of pixel rows A in the first segment 110 is indicated in therespective graph. The data signal output 152 for the second set of pixelrows B in the first segment 110 is indicated in the respective graph.The start time for the second set of pixel rows B in the first segment110 is the start time for the first set of pixel rows A in the firstsegment 110 as indicated in the signals 150 and 152. In the presentembodiment, the both start at t₀.

Similarly, since the first set of rows A and the second set of rows Bare alternatively disposed in the same grid segment, the data outputsignals for the first set (rows A) and the second set (rows B) arealternatively on and off such that the pattern generator is able toreceive proper signals for the A rows and B rows. Thus, the data outputsignal 150 for the rows A and the data output signal 152 for the rows Btogether constitute a collective data output signal for the firstsegment 110 (including both rows A and rows B) in a same sequence. Moreparticularly, the data output signal 150 is on while the data outputsignal 152 is off. The data output signal 150 is off while the dataoutput signal 152 is on. Sequentially, the data output signal 150 is on,off, on, off, . . . while the data output signal 152 is off, on, off,on, . . . .

The data signal output 154 for the first set of pixel rows C in thesecond segment 112 is t₀+2(2^(m)−1)*Δt₀+Δt. The data signal output 156for the second set of pixel rows D in the second segment 112 ist₀+2(2^(m)−1)*Δt₀+Δt (same as pixel rows C). Particularly, the starttime for the third set of pixel rows C in the second segment 112 is thesame start time for the second set of pixel rows D in the second segment112 as indicated in the signals 154 and 156.

Accordingly, the first set of pixel rows A in the first segment 110during the lithography process forms a data grid A with a same pixeldimension as the pixel dimension G of the pattern generator 108. Thesecond set of pixel rows B in the first segment 110 during thelithography process forms a data grid B with the same pixel dimension G.However, the data grid B is not only shifted from the data grid A in theX direction but also in the Y direction. A collective exposure dose fromboth the first set A and the second set B is defined by a data grid 140having a reduced pixel dimension in the X direction.

Similarly, the first set of pixel rows C in the second segment 112during the lithography process forms a data grid C with a same pixeldimension as the pixel dimension G of the pattern generator 108. Thesecond set of pixel rows D in the second segment 112 during thelithography process forms a data grid D with the same pixel dimension G.However, the data grid D is not only shifted from the data grid C in theX direction but also in the Y direction. A collective exposure dose fromboth the first set C and the second set D is defined by a data gridhaving a reduced pixel dimension in the X direction.

The data grid from the second segment 112 is different from the datagrid from first segment 110 since there is offset Δy=V*Δt in the Ydirection introduced by the time delay Δt. Furthermore, a collectiveexposure dose from both first segment 110 and second segment 112 isdefined by a data grid 142 having a reduced pixel dimension in the Xdirection and a reduced pixel dimension in the Y direction.

By implementing the pattern generator 108 and the method 130, withoutreducing the pixel size of the pattern generator, the data grid 142generated thereby has a reduced pixel size as G*n where G is the pixelsize of the pattern generator 108. The number of gray levels in eachpixel of the data grid 142 is Ny=2^(m)−1. The data volume is increasedby a factor m/n².

FIG. 7 is a schematic view of a method 160 for a lithography processwith reduced data grid for small CDs but without reducing the pixeldimensions of the pattern generator. Particularly, the data grid 162 isconverted to the alternating data grid 164 with reduced pixel size. Forexample, the data grid 162 has a pixel dimension G. The data grid 164 bythe method 160 has an alternating structure and has a pixel dimensionless than G. Thus, the grid reduction is achieved by the disclosedalternating data grid. In the data grid 164, two adjacent pixels withthe reduced pixel distance (less than G) span in a direction differentfrom X direction and Y direction as illustrated in FIG. 7. In method160, the data volume is increased only by a factor m/n or less, muchless than the factor m/n² achieved by the various methods in FIGS. 3, 4,5 and 6. The method 160 and the corresponding pattern generator arecollectively described with reference to FIGS. 8 and 9 according tovarious embodiments.

FIG. 8 is a schematic view of a method 170 for a lithography processwith reduced data grid for small CDs but without reducing the pixeldimensions of the pattern generator. The method 170 and thecorresponding pattern generator are collectively described withreference to FIG. 8 that includes a block 172 for pattern generator, ablock 174 for data grid and a block 176 for data signal output. It isstill assumed that the CD scales down by a factor n that is less than 1.In one example, the scaling factor n is 0.5.

In the method 170, a pattern generator 178 is used and includes aplurality of segments configured with shift and controlled with timedelay. The pattern generator 178 is designed to include a plurality ofsegments configured along the scan direction that is Y direction. Thepixels of the pattern generator 178 still remain the same pixeldimension G. In one example, the pixels have a square geometry and thedimensions of the pixels in both X and Y directions are G. In anotherembodiment, the pixels have a rectangular geometry 180, and thedimension of the pixels in X direction and the dimension of the pixelsin Y direction are different. For example, the dimension of the pixel inX direction is G and the dimension in Y direction is b*G where b isgreater than 1. Each segment includes a plurality of pixels in an array,such as an array with multiple rows each spanned in X direction andmultiple columns each spanned in Y direction. Furthermore, each rowincludes Nx pixels and each column includes Ny pixels. To achieve 2^(m)gray levels, the number of pixels in each column is 2^(m)−1 orNy=2^(m)−1. The similar features and actions are not described forsimplicity.

Each segment is shifted by a fraction of the pixel dimension along thedirection perpendicular to the scan direction and is also controlled tohave delayed data signal output. In one example, each segment is shiftedby n*G along the direction perpendicular to the scan direction and isalso controlled to have delayed data signal output by n*G/v where v isthe scan speed.

In the present example for illustration, the pattern generator 178includes 2 segments labeled as A and B, respectively. In this example,the segment B is shifted from the segment A by Δx and is controlled tohave a time delay Δt.

However, the pattern generator 178 is different from other patterngenerators presented in FIGS. 3, 4, 5 and 6 as explained below. Thereduction to the data grid is achieved but fewer segments are used andtherefore less data volume is accomplished. In the pattern generator 48or 78, four segments or 1/n² segments are included. In either situation,the data volume is increased by the factor m/n². In the patterngenerator 178, two segments or 1/n segments are included and eachsegment remains the same size or the same number of pixels as Nx*Nywherein Ny=2^(m)−1. Therefore, the data volume is increased only by m/ninstead of m/n².

The segment B is configured to have an offset from the segment A by adistance Δx in the X direction and is controlled to have a time delay Δtduring the lithography process, causing exposure dose shifted in the Ydirection by Δy=V*Δt. In one example, each of Δx and Δy is 0.5G or n*G.

The data signal output 186 for the first segment A is indicated in therespective graph. The data signal output 188 for the second segment B ist₀+(2^(m)−1)*Δt₀+Δt as indicated in the respective graph.

Accordingly, the first segment A during the lithography processgenerates an exposure dose defined by a data grid 182 with a same pixeldimensions as the pixel dimensions of the pattern generator 178. Thesecond segment B during the lithography process forms an exposure dosedefined by a data grid B with the same pixel dimensions but with a shiftΔx in X direction and a shift Δy in Y direction. A collective exposuredose from both the segment A and the segment B is defined by a data grid184 having a reduced pixel dimensions as illustrated in 185.

By implementing the pattern generator 178 and the method 170, withoutreducing the pixel size of the pattern generator, the data grid 182generated thereby has a reduced pixel dimension <G where G is the pixeldimension of the pattern generator 178. The number of gray levels ineach pixel of the data grid 184 is Ny=2^(m)−1. The data volume isincreased only by a factor m/n.

FIG. 9 is a schematic view of a method 190 for a lithography processwith reduced data grid for small CDs but without reducing the pixeldimensions of the pattern generator. The method 190 and thecorresponding pattern generator are collectively described withreference to FIG. 9 that includes a block 192 for pattern generator, ablock 194 for data grid and a block 196 for data signal output. It isstill assumed that the CD scales down by a factor n that is less than 1.In one example, the scaling factor n is 0.5.

In the method 190, a pattern generator 198 is used and includes aplurality of segments configured with shift and controlled with timedelay. The pattern generator 198 is designed to include a plurality ofsegments configured along the scan direction that is Y direction. Thepixels of the pattern generator 198 still remain the same pixeldimension G. In one example, the pixels have a square geometry and thedimensions of the pixels in both X and Y directions are G. In anotherembodiment, the pixels have a rectangular geometry 200, and thedimension of the pixels in X direction and the dimension of the pixelsin Y direction are different. For example, the dimension of the pixel inX direction is G and the dimension in Y direction is b*G where b isgreater than 1. Each segment includes a plurality of pixels in an array,such as an array with multiple rows each spanned in X direction andmultiple columns each spanned in Y direction. Furthermore, each rowincludes Nx pixels and each column includes Ny pixels. However, the graylevels is reduced from 2^(m) to 2^((m-a)), and the number of pixels ineach column is 2^(m-a)−1 or Ny=2^(m-a)−1. The parameter “a” is greateror equals to 0.

Each segment is shifted by a fraction of the pixel dimension along thedirection perpendicular to the scan direction and is also controlled tohave delayed data signal output.

In the present example for illustration, the pattern generator 198includes 2 segments labeled as A and B, respectively. In this example,the segment B is shifted from the segment A by Δx and is controlled tohave a time delay Δt. The pattern generator 198 is similar to thepattern generator 178 but the number of the pixels in each column isreduced. Accordingly, the number of the gray levels is reduced and thedata volume is reduced.

The segment B is configured to have an offset from the segment A by adistance Δx in the X direction and is controlled to have a time delay Δtduring the lithography process, causing exposure dose shifted in the Ydirection by Δy=V*Δt.

The data signal output 206 for the first segment A is indicated in therespective graph. The data signal output 208 for the second segment B ist₀+(2^(m-a)−1)*Δt₀+Δt as indicated in the respective graph.

Accordingly, the first segment A during the lithography processgenerates an exposure dose defined by a data grid 202 with a same pixeldimensions as the pixel dimensions of the pattern generator 198. Thesecond segment B during the lithography process forms an exposure dosedefined by a data grid B with a same pixel dimensions but with a shiftΔx in X direction and a shift Δy in Y direction. A collective exposuredose from both the segment A and the segment B is defined by a data grid204 having a reduced pixel dimensions as illustrated in 205.

By implementing the pattern generator 198 and the method 190, withoutreducing the pixel size of the pattern generator, the data grid 204generated thereby has a reduced pixel size. The number of gray levels isNy=2^(m-a)−1. The data volume is increased only by a factor (m−a)/n.

FIG. 10 is a schematic view of a data grid and the respective datasignal output. The data grid 210 is, in portion, the data grid 56 ofFIG. 3, the data grid 86 of FIG. 4, the data grid 184 of FIG. 8, or thedata grid 204 of FIG. 9, constructed according to one embodiment. Thedata grid 212 is portion of the data grid 210 zoomed in. Thecorresponding coordinates for the pixels in the data grid 212 areillustrated in 214, for an example where 1/n=3.

The data signal output is determined by the formula

t = t₀ + (l − 1)(2^((m − a)) − 1)Δ t₀ + y Δ t${l \in {\left. 1 \right.\sim\frac{1}{n^{2}}}},{a \geq 0}$where y is the coordinate of the respective pixel in the data grid. Theformula can be used to determine the data signal output in variousmethods 40, 70, 170 and 190, corresponding to the data grids 56, 86, 184and 204, respectively.

Furthermore, the data grid 212 has the size corresponds to one pixel ofthe respective pattern generator. The pixel dimension of the data grid212 is reduced from the respective pixel dimension of the patterngenerator. The pixel area S₂ of the data grid 212 is reduced from therespective pixel area S₁ of the pattern generator. In one embodimentrelated to the data grid 56 of FIG. 3 and the data grid 86 of FIG. 4,the pixel area S₂ of the data grid 212 is reduced from the respectivepixel area S₁ of the pattern generator by a factor n² as S₂=n²*S₁. Inanother embodiment related to the data grid 184 of FIG. 8, or the datagrid 204 of FIG. 9, the pixel area S₂ of the data grid 212 is reducedfrom the respective pixel area S₁ of the pattern generator such asS₂<S₁. The pattern generator is segmented into a plurality of gridsegments (or segments). The segments of the pattern generator areconfigured to have a shift in a direction (X direction) perpendicular tothe scan direction and/or are controlled to have time delay to introducea shift on the scan direction (Y direction) during the lithographyprocess.

In one embodiment, the pattern generator is segmented to 1/n² segments,such as those illustrated in FIGS. 3 and 4. Segments may have a shift inthe X direction or a time delay. Each segment have a number of pixelsNx*Ny where Ny=2^(m-a)−1. The data volume is increased by a factor(m−a)/n². The gray levels are reduced from 2^(m) to 2^(m-a). In oneexample, the parameter a=0. In another example, the parameter “a” is aninteger greater than 0 but less than m. In the example illustrated inFIG. 10, n=⅓. In other examples illustrated in FIGS. 3 and 4, n=½ (or0.5).

In another embodiment, the pattern generator is segmented to n segments,such as those illustrated in FIGS. 8 and 9. Each segment has a shift inthe X direction and a time delay. The data volume is increased by afactor (m−a)/n. the gray levels are reduced from 2^(m) to 2^(m-a).

FIG. 11 is a schematic view of a data grid and the respective datasignal output. The data grid 220 is, in portion, the data grid 116 ofFIG. 5, constructed according to one embodiment. The data grid 222 isportion of the data grid 220 zoomed in. The corresponding coordinatesfor the pixels in the data grid 222 are illustrated in 224, for aparticular example where 1/n=3.

The data signal output is determined by the formula

$t = {t_{0} + {\left( {{\frac{y}{n}\left( {2^{({m - a})} - 1} \right)} + x} \right)\Delta\; t_{0}} + {y\;\Delta\; t}}$a ≥ 0where x and y are the coordinates of the respective pixel in the datagrid. The formula can be used to determine the data signal output in themethod 100, corresponding to the data grid 116.

Furthermore, the data grid 222 has the size corresponds to one pixel ofthe respective pattern generator. The pixel dimension of the data grid222 is reduced from the respective pixel dimension of the patterngenerator by a factor n. The pixel area of the data grid 222 is reducedfrom the respective pixel area of the pattern generator by a factor n².The pattern generator is segmented into a plurality of grid segments (orsegments). The segments of the pattern generator are controlled to havetime delay to introduce a shift on the scan direction (Y direction)during the lithography process. Each segment has an alternatingstructure and has a number of pixels increased by a factor 1/n. Eachsegment has the number of pixels Nx*Ny where Ny=n*(2^(m-a)−1). Pixelrows in each segment are grouped into 2^(m-a)−1 groups. Each groupincludes n pixel rows. The pixel rows in each group are configuredadjacent with each other and each row has a shift relative to itsadjacent row in the X direction perpendicular to the scan direction. Thedata volume is increased by a factor (m−a)/n² or m/n² if a=0. The graylevels are reduced from 2^(m) to 2^(m-a).

FIG. 12 is a schematic view of a data grid and the respective datasignal output. The data grid 230 is, in portion, the data grid 142 ofFIG. 6, constructed according to one embodiment. The data grid 232 isportion of the data grid 230 zoomed in. The corresponding coordinatesfor the pixels in the data grid 232 are illustrated in 234, for aparticular example where 1/n=3.

The data signal output is determined by the formula

$t = {t_{0} + {\left\lbrack {\left( {\frac{1}{n} - 1} \right) + y} \right\rbrack\left( {2^{({m - a})} - 1} \right)\Delta\; t_{0}} + {y\;\Delta\; t}}$a ≥ 0The formula can be used to determine the data signal output in themethod 130, corresponding to the data grid 146.

Furthermore, the data grid 232 has the size corresponds to one pixel ofthe respective pattern generator. The pixel dimension of the data grid232 is reduced from the respective pixel dimension of the patterngenerator by a factor n. The pixel area of the data grid 232 is reducedfrom the respective pixel area of the pattern generator by a factor n².The pattern generator is segmented into a plurality of grid segments (orsegments). The segments of the pattern generator are controlled to havetime delay to introduce a shift on the scan direction (Y direction)during the lithography process. Each segment has an alternatingstructure and has a number of pixels increased by a factor 1/n. Eachsegment has the number of pixels Nx*Ny where Ny=n*(2^(m-a)−1). Pixelrows in each segment are grouped into 2^(m-a)−1 groups. Each groupincludes n pixel rows. The pixel rows in each group are configuredadjacent with each other and each row has a shift relative to itsadjacent row in the X direction perpendicular to the scan direction. Thedata volume is increased by a factor (m−a)/n² or m/n² if a=0. The graylevels are reduced from 2^(m) to 2^(m-a).

The present disclosure provides one embodiment of a method for alithography process for reducing a critical dimension (CD) by a factor nwherein n<1. The method includes providing a pattern generator having afirst pixel size S1 to generate an alternating data grid having a secondpixel size S2 that is <S1, wherein the pattern generator includesmultiple grid segments configured to offset from each other in a firstdirection; and scanning the pattern generator in a second directionperpendicular to the first direction during the lithography process suchthat each subsequent segment of the grid segments is controlled to havea time delay relative to a preceding segment of the grid segments.

In one embodiment of the method, the pattern generator includes a numberof pixels increased by a factor n and a data volume to the patterngenerator, the data volume being proportional to 1/n.

In another embodiment, the pattern generator is designed to generate2^(m) gray levels, and a data volume to the pattern generator isproportional to m/n.

In yet another embodiment, the pattern generator is designed to have areduced gray levels from 2^(m) to 2^(m-a), parameter “a” being greaterthan 0 and a data volume to the pattern generator is proportional to(m−a)/n.

In yet another embodiment, a number of the grid segments in the patterngenerator equals to 1/n. In one embodiment, each of the grid segmentsincludes a grid array with (2^(m)−1) pixels in each column spanned inthe second direction and the alternating data grid has 2^(m) graylevels. In another embodiment, each of the grid segments includes a gridarray with (2^(m-a)−1) pixels in each column spanned in the seconddirection and the alternating data grid has 2^(m-a) gray levels,parameter a being greater than 0.

The present disclosure also provide one embodiment of a patterngenerator for a lithography process to form an exposure dose defined ina alternating data grid for reducing a critical dimension (CD) by afactor n wherein n<1. The pattern generator includes a plurality of gridsegments configured to offset from each other in a first direction andis controllable to have a time delay during the lithography process; anda plurality of pixels arranged in the grid segments, wherein a number ofthe pixels is increased by a factor 1/n.

In one embodiment, the pattern generator is designed to generate 2^(m)gray levels, and a data volume to the pattern generator is proportionalto m/n.

In another embodiment, the pattern generator is designed to have areduced gray levels from 2^(m) to 2^(m-a), parameter “a” being greaterthan 0 and a data volume to the pattern generator is proportional to(m−a)/n.

In yet another embodiment, the plurality of pixels in the grid segmentseach include a shape of square or rectangle.

In yet another embodiment, a number of the grid segments in the patterngenerator equals to 1/n. In one embodiment, each of the grid segmentsincludes a grid array with (2^(m-a)−1) pixels in each column spanned inthe second direction and the alternating data grid has 2^(m-a) graylevels, parameter a being equal to or greater than 0.

The present disclosure also provides another embodiment of a method fora lithography process to form an exposure dose defined in an alternatingdata grid having a first pixel dimension using a pattern generatorhaving a second pixel dimension greater than the first pixel dimensionby a scaling factor 1/n where the scaling factor is less than 1. Themethod includes receiving the pattern generator having multiple gridsegments configured to offset from each other in a first direction; andperforming an exposure process to a substrate and thereby form a circuitpattern on the substrate. The performing of the exposure processincludes scanning the pattern generator in a second directionperpendicular to the first direction; and controlling the grid segmentssuch that each of the grid segments has a time delay during the scanningof the pattern generator.

In one embodiment of the method, the pattern generator has a number ofpixels increased by a factor 1/n and a data volume to the patterngenerator, the data volume being proportional to 1/n.

In another embodiment, the pattern generator is designed to generate2^(m) gray levels, and a data volume to the pattern generator isproportional to m/n.

In yet another embodiment, the pattern generator is designed to have areduced gray levels from 2^(m) to 2^(m-a), parameter “a” being greaterthan 0; and a data volume to the pattern generator is proportional to(m−a)/n.

In yet another embodiment, a number of the grid segments in the patterngenerator equals to 1/n. In one embodiment, each of the grid segmentsincludes a grid array with (2^(m)−1) pixels in each column spanned inthe second direction and the alternating data grid has 2^(m) graylevels. In another embodiment, each of the grid segments includes a gridarray with (2^(m-a)−1) pixels in each column spanned in the seconddirection and the alternating data grid has 2^(m-a) gray levels,parameter a being greater than 0.

In yet another embodiment, the performing an exposure process to asubstrate includes applying an e-beam to the pattern generator.

In yet another embodiment, the controlling the grid segments such thateach of the grid segments has a time delay during the scanning of thepattern generator includes applying to the pattern generator by a datasignal output defined in a formula as

t = t₀ + (l − 1)(2^((m − a)) − 1)Δ t₀ + y Δ t${l \in {\left. 1 \right.\sim\frac{1}{n^{2}}}},{a \geq 0}$

The foregoing outlines features of several embodiments so that thoseskilled in the art may better understand the aspects of the presentdisclosure. Those skilled in the art should appreciate that they mayreadily use the present disclosure as a basis for designing or modifyingother processes and structures for carrying out the same purposes and/orachieving the same advantages of the embodiments introduced herein.Those skilled in the art should also realize that such equivalentconstructions do not depart from the spirit and scope of the presentdisclosure, and that they may make various changes, substitutions, andalterations herein without departing from the spirit and scope of thepresent disclosure.

What is claimed is:
 1. A lithographic method comprising: receiving apattern to be transferred to a photoresist film by a pattern generator,wherein a plurality of pixels are defined for the pattern generator,wherein the plurality of pixels are arranged in a plurality of pixelrows, and wherein a first pixel row of the plurality of pixels rows isoffset from a second pixel row of the plurality of pixel rows in a firstdirection by less than a pixel size; and determining pixel values forthe plurality of pixels such that a collective exposure dose thatincludes a dose from the first pixel row and a dose from the secondpixel row satisfies an exposure dose specified by the pattern.
 2. Thelithographic method of claim 1 further comprising: exposing thephotoresist film using the pattern generator according to the pixelvalues such that a portion of the photoresist film is exposed accordingto each of the first pixel row and the second pixel row.
 3. Thelithographic method of claim 1, wherein the portion of the photoresistfilm is exposed according to each pixel of the first pixel row and eachpixel of the second pixel row.
 4. The lithographic method of claim 1,wherein the pixel values for the plurality of pixels are furtherdetermined such that the collective exposure dose that includes a dosefrom each pixel of the first pixel row and a dose from each pixel of thesecond pixel row satisfies the exposure dose specified by the pattern.5. The lithographic method of claim 1, wherein the second pixel row isfurther offset from the first pixel row in a second direction by anamount less than the pixel size.
 6. The lithographic method of claim 1,wherein the plurality of pixel rows further includes a third pixel rowand a fourth pixel row, wherein the third pixel row is offset from thefirst pixel row by less than the pixel size in a second direction, andwherein the fourth pixel row is offset from the first pixel row by lessthan the pixel size in the first direction and by less than the pixelsize in the second direction.
 7. The lithographic method of claim 6,wherein the pixel values for the plurality of pixels are furtherdetermined such that a collective exposure dose that includes a dosefrom the first pixel row, a dose from the second pixel row, a dose fromthe third pixel row, and a dose from the fourth pixel row satisfies theexposure dose specified by the pattern.
 8. The lithographic method ofclaim 1, wherein an amount of offset between the first pixel row and thesecond pixel row is determined by a reduction in a critical dimensionbetween technology nodes.
 9. A method of lithographically exposing asubstrate, the method comprising: receiving, at a pattern generator,pixel values for a first pixel row and a second pixel row, wherein thesecond pixel row is offset from the first pixel row in a first directionby an amount less than a pixel width; exposing a portion of thesubstrate by scanning a beam across the portion during a first pass,wherein the intensity of the beam varies according to the pixel valuesof the first pixel row; and exposing the portion of the substrate byscanning the beam across the portion during a second pass, wherein theintensity of the beam varies according to the pixel values of the secondpixel row.
 10. The method of claim 9, wherein the pixel values of thefirst pixel row and the second pixel row are determined such that acollective exposure dose including a dose of the first pixel row and adose of the second pixel row satisfies an exposure dose specified by acircuit pattern.
 11. The method of claim 9, wherein the portion of thesubstrate is exposed according to each pixel of the first pixel row andeach pixel of the second pixel row.
 12. The method of claim 11, whereinthe pixel values of the first pixel row and the second pixel row aredetermined such that a collective exposure dose including a dose fromeach pixel of the first pixel row and a dose from each pixel of thesecond pixel satisfies an exposure dose specified by a circuit pattern.13. The method of claim 9, wherein the second pixel row is furtheroffset from the first pixel row in a second direction by less than apixel length.
 14. The method of claim 9 further comprising: receiving,at the pattern generator, pixel values for a third pixel row and afourth pixel row, wherein the third pixel row is offset from the firstpixel row in a second direction by an amount less than a pixel length,and wherein the fourth pixel row is offset from the first pixel row inthe first direction by an amount less than the pixel width and in thesecond direction by an amount less than the pixel length.
 15. The methodof claim 14, wherein the pixel values of the first pixel row, the secondpixel row, the third pixel row, and the fourth pixel row are determinedsuch that a collective exposure dose including a dose of the first pixelrow, a dose of the second pixel row, a dose of the third pixel row, anda dose of the fourth pixel row satisfies an exposure dose specified by acircuit pattern.
 16. A method for a lithographic process, the methodcomprising: receiving a circuit pattern to be formed on a substrate by apattern generator, determining pixel values for a first pixel row and asecond row of the pattern generator such that a collective exposure dosethat includes a dose from the first pixel row and a dose from the secondpixel row satisfies an exposure dose specified by the circuit pattern;exposing the substrate according to the first pixel row; and exposingthe substrate according to the second pixel row using a time delay suchthat the second pixel row is offset from the first pixel row by anamount less than a pixel size in a first direction and such that aportion of the substrate is exposed according to each of the first pixelrow and the second pixel row.
 17. The method of claim 16 furthercomprising: determining pixel values for a third pixel row and a fourthrow of the pattern generator such that the collective exposure dose thatfurther includes a dose from the third pixel row and a dose from thefourth pixel row satisfies the exposure dose specified by the circuitpattern; exposing the substrate according to the third pixel row using atime delay such that the third pixel row is offset from the first pixelrow by an amount less than the pixel size in a second direction; andexposing the substrate according to the fourth pixel row using a timedelay such that the fourth pixel row is offset from the first pixel rowby an amount less than the pixel size in the first direction and anamount less than the pixel size in the second direction.
 18. The methodof claim 17, wherein the portion of the substrate is further exposedaccording to each of the third pixel row and the fourth pixel row. 19.The method of claim 17, wherein the portion of the substrate is exposedaccording to each pixel within each of the first pixel row, the secondpixel row, the third pixel row, and the fourth pixel row.
 20. The methodof claim 17, wherein the time delay is determined by a reduction in acritical dimension between technology nodes.